Cigarette smoking continues to be the leading cause of preventable death, disease, and excess health cost in the United States. Cigarette smokers with Posttraumatic Stress Disorder (PTSD) represent a common, albeit understudied, segment of the smoking population who may be at heightened risk for continued nicotine dependence and its associated morbidity and mortality . The impact of PTSD on smoking cessation outcomes has yet to be empirically examined. The present proposal aims to fill this gap by examining the extent to which PTSD is associated with decreased success in a self-guided quit attempt among regular smokers. The proposed study will employ a prospective design that will follow a sample of 84 smokers for three months as they attempt to quit smoking on their own. Half of the sample will meet criteria for PTSD and the other half will have no psychiatric disorder. Prior to their cessation attempt, participants will complete a diagnostic interview and measures assessing psychological functioning and smoking characteristics. Beginning on quit day and continuing at one, two, four, and twelve weeks after the quit date, participants will return to the study center for biochemical verification of smoking status, as well as assessment of smoking outcomes, psychological functioning, and withdrawal symptoms. The first hypothesis is that smokers with PTSD compared to smokers without a psychiatric diagnosis will demonstrate less success in a self-guided cessation attempt. This will be indexed by: (a) shorter time to first smoking lapse and (b) lower point prevalence abstinence at one, two, four, and twelve weeks after the quit date. The second hypothesis is that smokers with PTSD compared to smokers without a psychiatric diagnosis will demonstrate elevated self-reported negative affect during the initial week of cessation from smoking. The present proposal seeks to test the extent to which PTSD interferes with smoking cessation, and identify theoretically relevant negative emotional processes that impede smoking cessation. Findings from this investigation will help guide future efforts to develop specialized treatment strategies for smokers with PTSD, a population at high risk for nicotine dependence.